The present invention relates to a static random access memory (referred to as RAM hereinbelow) and, more particularly, to a static RAM in which a pair of inverters are cross-coupled to form a memory element of a flip-flop.
Conventional static RAMs comprise memory elements of flip-flops in which a memory operation is enabled in accordance with an ON/OFF application of a current. FIGS. 1(A) to 1(C) show the conventional RAMs in which a pair of inverters are cross-coupled to form a flip-flop as a data storage element. The difference among the cells of FIGS. 1(A) to 1(C) lies in that a load element of the flip-flop is a high resistance element (FIG. 1(A)), an enhancement-type MOS transistor (FIG. 1(B)), and a depletion-type MOS transistor (FIG. 1(C)).
All the cells of FIGS. 1(A) to 1(C) contain two transfer gate MOS transistors for reading/writing data. Each of the transfer gate MOS transistors is allotted to a data line bearing a high level, and another data line bearing a low level signal.
Therefore, it is desired to reduce the number of elements for forming the static RAM to enhance the integration.